Spitting image

Strictly speaking, 'spitting image' should never appear with this spelling because it is a corruption of 'spit and image'. If the expression is said quickly, it sounds like 'spit 'n image' and in US dialect it often appears as 'spitten image'. Nevertheless, 'spitting image' meaning an exact likeness, as in ‘he is the spitting image of his father’, first appears in this 'incorrect' form from the early 20th century. According to the OED, 'spit' meaning an exact likeness is a British colloquialism, dating from 1825, and is used in expressions like 'he is the spit and image of his father’ or ‘he is the very spit of his father’. Thus, the progression from ‘spit and image’ to the current, but strictly incorrect, ‘spitting image’ has taken about 75 years, but is still frowned upon by English grammar purists.